Study on Electrical Measurement Method of AC Loss in Oxide High Tc Superconducting Magnet

超导磁体已经被研究，以扩大新的技术领域。目前，低T_c超导线材已基本达到实用化水平。相反，高T_c超导线材(HTSW)比低温超导线材(HTSW)更具优势，因为可以使用液氮进行冷却。长丝长丝的高温短波最近已经制造出来，预计未来将从低温短波向高温短波转变。掌握超导磁体的交流损耗是非常重要的，因为交流损耗本质上是在超导导线中产生的。在本研究中，开展了与超导磁体交流损耗评估相关的相位差测量。提出了三种测量超导磁体相位差的方法，并对其进行了测量。首先，利用高温超导材料Bi2223多丝制作了双薄饼线圈的超导磁体。接下来，使用交流电源对磁体进行激磁测试。结果表明，磁体的电压和电流之间的相位差几乎接近90°。最后，利用三种类型的电子电路对超导磁体的相位差进行了测量。特别是利用运算放大器对电子电路的测量结果与锁相放大器的测量结果吻合较好，因此认为该电子电路是实用的。

Superconducting magnets have been studied to extend the new technology region. At present, low T_c superconductive wire (LTSW) has almost reached the level of practical use. In contrast, high T_c superconductive wire (HTSW) is more advantageous than LTSW, because it is possible to use liquid nitrogen in the cooling. The HTSW of long-length multi filaments has recently been manufactured, and a shift from LTSW to HTSW is expected in the future. A grasp of AC loss for the superconducting magnet is very important, since the AC loss is essentially generated in the superconducting wire.In this research, the phase difference measurement, which is related to the evaluation of the AC loss of the superconducting magnet, was carried out. The methods of three types were proposed to measure the phase difference of the superconducting magnet and the measurement of the phase difference was performed.First, the superconducting magnet of a double pancake coil was constructed using HTSW with Bi-2223 multi filaments. Next, an exciting test of the magnet using the AC power supply was performed. As a result, it was confirmed that the phase difference between the voltage and the current of the magnet almost approximated 90°. Finally, the phase difference of the superconducting magnet was measured using the electronic circuits of three types. Especially, the measuring result of the electronic circuit using op-amps agrees with the result by a lock-in amplifier comparatively well, and thus it is considered that the electronic circuit is practical.